This is an informative take on the Nili Fossae region; almost certainly, Perseverance's discoveries will have some relevance in confirming or rebutting some of the suppositions found here.

https://marsnext.jpl.nasa.gov/documents/Lan...ossae_final.pdf

I look at this akin to the Lost City carbonate mounds (hydrothermal field) on the northwest Altlatic ocean on Earth. "Cold water" hydrothermal activity will do well. This is adjacent to the Syrtis (now called Nili?) Volcanic province, with an extensive fracture system from the Isis impact.
But the big story will be to study the deltaic facies of the Jezero Delta, and look for organic traces. We've gotten so tunnel-visioned with these first lake-bottom favors we've encountered.
I'm looking forward to the adventure of the forthcoming year!

--Bill

Rather than a one size fits all scenario for the formation of the carbonates it is probable that there were a number of pathways. The environment at the time is not clear and there are indications for marginal deposits, either for the Jezero lake or for the Northern ocean if it did exist, as seems likely. The extent of such an ocean in the Nili Fossae region, possibly with associated precipitation is uncertain.

Julius suggestion of methane as a key greenhouse gas on early mars is problematic as its absorption band peaks at 1300 cm−1, well above the the blackbody blackbody emission spectrum peak at 250–300 K and the contribution to warming would seem insufficient. There has been some discussion on whether CO2 –H2 and CO2 –CH4 collision-induced absorption could increase the effectiveness of the greenhouse effect. But the warming mechanism remains a mystery.

[attachment=49090:ped_climb.JPG]

And we have almost arrived at the pediment already! The resistant capstone at the top of the cliff in front of us is indeed the Greenheugh pediment I have overlaid the MSAR_10 route (the most recent strategic route) to show roughly where the team probably intends to ascend up onto the pediment. From the looks of the planned traverse, the rover will follow this cliff uphill, squeezing through a narrow passage and then ascending a ramp. However, before all that I expect they'll want to drill nearby to where we are now, to document the chemistry of the rocks directly underneath the pediment. Once we're ontop, the view will be very special. Looks like they plan on sending the rover towards that big ridge that runs down the middle of it - my understanding is that there's debate over whether the Greenheugh pediment represents just aeolian sandstones, basically a lateral continuation of the stimson formation (remember the buttes all those years ago?), alternatively it might be an alluvial fan. It certainly resembles a fan in shape and that big ridge running down the middle could be an inverted channel. This is why the mission geologists want to send the rover there, to check which theory's true!